A green and efficient way to improve sugar recovery of wheat straw by ultrasonic-assisted xylanase pretreatment

The cost-effectiveness of bioethanol production from wheat straw (WS) has been hindered by low sugar yield and high manufacturing cost. In this research, an ultrasonic-assisted xylanase (UX) pretreatment of WS was developed to enhance sugar recovery with low energy cost. The proposed method provides several benefits, including the following: (i) the surface roughness of WS was remarkably increased with ultrasonic at room temperature, which has provided more catalytic sites for xylanase; (ii) the hemicellulose and lignin barriers around cellulose were efficiently removed with xylanase pretreatment; and (iii) the accessibility of cellulose and sugar recovery of WS were improved under mild conditions. Under optimized conditions, a maximum of 69.1% hemicellulose removal and 49.7% delignification were attained with UX pretreatment, resulting in glucose yield five-fold that of raw wheat straw. FT-IR, XRD, TGA, SEM, and CLSM were used to characterize the samples before and after pretreatment. The results show that the UX pretreatment significantly improved the accessibility of cellulose.